Six novel murine homeobox genes, Uncx-4.1, OG-2, OG-9, OG-12, OG-22, and NKx were cloned and partially sequenced. Two OG-12 cDNAs were cloned that correspond to alternatively spliced species of OG-12 mRNA. More than ten kb of NKx genomic DNA were sequenced. Northern blot hybridization of NKx poly-A+ RNA from adult mouse tissues revealed one major band of NKx RNA in brain and multiple bands in testes. Nkx mRNA was found in the mesencephalon, myelencephalon, spinal cord, vertebrae, and ribs of 12 day mouse embryos, and in distinct patches in the pons and diencephalon of 14 day mouse embryos. Two species of OG-22 cDNA were found in mouse embryo cDNA libraries that correspond to alternatively spliced species of OG-22 mRNA. OG-22 mRNA is expressed in the head and brachial arches of mouse embryos, and in adult mouse lung and testis.